This research project will study mammalian fertilization, focusing on identifying molecules that mediate the binding and fusion of gamete plasma membranes. Relatively little is known about this developmental timepoint. Recently, a putative ligand on sperm was identified in guinea pig, known as PH-30. However, since the guinea pig system is very intractable for the study of fertilization and egg activation, this research will study the mouse homolog of PH-30, since the mouse system is well-characterized and easy to use. The project has two stages. The first stage will generate reagents that will be used in future experiments; methods used will include isolation of clones from a cDNA library, expression of recombinant protein, and production of antibodies. The second stage of the project will use these reagents to determine if PH-30 binds to eggs, if PH-30 or anti-PH-30 antibodies can inhibit in vitro fertilization, and if specific egg membrane proteins bind to PH-30 in chemical cross-linking experiments. This work has direct applications in the research of assisted fertility treatments and contraceptive techniques.